Dear Labmembers,
I am looking for a purely solvent-based photoresist/developer
combination, so that the fragile spin valves (magnetoresistive sensors)
on my wafer are not exposed to the alkaline developer LDD26W, which can
severely corrode their very fine and essential copper layer. LDD26W
etches Aluminum at a rate of roughly 30 nm per minute, and copper even
faster - once when I tried to make a copper hard mask, the LDD26W
literally tore through the copper film even before the resist
development was complete.
I need to fabricate metallic leads for these copper-film containing spin
valves by means of a lift-off process, and where these leads overlap
with the sensors, the opening in the resist exposes the sensors to the
developer, quite possibly damaging them in the process. This may be a
concern especially for submicron sensors - the smaller the sensors, the
shorter the time they can withstand immersion in a corrosive environment.
On the other hand, the required feature size is quite lenient - 2 micron
should suffice for the lead mask. This means a "coarse" process or
resist would be o.k.
In summary:
- Solvent-based resist & developer for optical photolithography
- Avoids alkaline or corrosive aqueous solutions
- Suitable for lift-off of up to 300 nm metal (bilayer if possible)
- Coarse resolution (cd = 2 microns) is o.k.
Please let me know if you have a working recipe.
Thanks!
--
Sebastian J. Osterfeld
PhD. Student / Shan X. Wang Group
Dept. of Materials Science & Engineering